<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        ul,li{
            margin: 0;
        }
        .box{
            width: 800px;
            border: 1px solid #000;
            position: relative;
        }
        .box .right{
            width: 480px;
            background-color: pink;
            margin-left: 320px;
        }
        .left{
            position: absolute;
            width: 300px;
            background-color: skyblue;
            top: 0;
            bottom: 0;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="left">1111</div>
        <div class="right">
            <ul>
                <li>1</li>
                <li>2</li>
                <li>3</li>
                <li>4</li>
                <li>5</li>
                <li>6</li>
                <li>7</li>
            </ul>
        </div>
    </div>
</body>
</html>